Lawsonia intracellularis

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Overview


Characteristics

  • Slender, curved, Gram negative rod
  • Microaerophilic
  • Obligate intracellular bacterium
  • Requires enterocyte tissue culture for growth


Pathogenesis and pathogenicity

  • Affinity for porcine enterocytes
  • Causes proliferation of enterocytes
  • Adenomatous and inflammatory lesions develop in the terminal ilium, caecum and colon
  • Synergistic relationship between L. intracellularis and intestinal flora including E. coli, Clostridium species and Bacteroides species
  • Intestinal organisms may produce correct oxygen tension and conditions for colonisation of L. intracellularis
  • Infection can only take place in presence of intestinal flora


Clinical disease

  • Proliferative enteropathy occurs in weaned pigs, 6-12 weeks old
  • Chronic intermittent diarrhoea with reduced growth or acute haemorrhagic enteropathy
  • Sudden heath in severe infections
  • Recovery from mild form in most animals without treatment
  • Post mortem lesions include thickened wall, mucosal necrosis with clotted blood in the lumen of the ilium, caecum and colon
  • Enlarged mesenteric lymph nodes


Diagnosis

  • Clinical signs and pathology give a presumptive diagnosis
  • Organisms demonstrated in faeces or ileal mucosa by immunofluorescence or PCR
  • Silver impregnation stains or immunostaining or lesions
  • Culture in enterocyte cell lines


Treatment and control

  • Antibiotics such as tylosin, tiamulin used prophylactically or therapeutically in feed/water
  • Zinc bacitracin in feed
  • Thorough cleaning and disinfection of premises